[Dune] Semantics of GlobalID set in Dune Grid API ?

[Christian Engwer]

Dear Benedikt,

> Dear Dune developers, we are currently experiencing problems with parallelizing our electromagnetic code.
>
> The specific question that arises is: we need to define a direction on all edges of the parallel, distributed mesh.
> We use ALUGrid for this. The reason for this is that the Whitney elements are associated with the edges rather
> than the vertices of a mesh. In oder to evaluate the basis function consistently over interprocessor boundaries,
> we use a Global ID set on the vertices. The Dune docu says they are globally unique over the distributed mesh.
> 
> The precise question is: does a vertex that belongs to an edge on the interprocessor boundary have
> THE SAME ID ON BOTH PROCESSORS ? This is important because we define the positive direction of
> an edge like this: positiv is from the vertex with the lower ID to the vertex with the higher ID.
> Thus, the positive direction is the same ON ALL PROCESSORS.

That was the idea of the global ID. It was designed to provide means
of identification the same entity on different processes.

As you are referring explicitly to alugrid... I didn't test it with
alugrid, but I'd be surprised, if there is a bug in this particular
feature.

Cheers Christian

> If this is not the case, then even using globally unique Id's may not guarantee the uniqueness
> of the positive direction definition of the edges.
> 
> Answers to this are highly appreciated, as alway!
> 
> I hope I made the problem clear ?
> 
> Have a great day, Benedikt
> 
> 
> 
> 
> ------------------------------------------------------------------------------------------------------------------
> Benedikt Oswald, Dr. sc. techn., dipl. El. Ing. ETH, www.psi.ch, Computational Accelerator Scientist
> Paul Scherrer  Institute (PSI), CH-5232 Villigen, Suisse, benedikt.oswald at psi.ch, +41(0)56 310 32 12
> "Passion is required for any great work, and for the Revolution passion and audacity are required in big doses.", 
> Ernesto 'Che' Guevara, Letter to his parents.
> http://maxwell.psi.ch/amaswiki/index.php/User:BenediktOswald 
> ------------------------------------------------------------------------------------------------------------------
> 
> 
> 
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